1. Field of the Invention
The present invention relates to a rock drill including a drill stem having an end face, major cutting edges extending substantially over a diameter of the drill stem and projecting beyond the end face, and at least one minor cutting edge extending substantially in a radial direction and provided on at least one elongate cutting body which projects beyond the end face of the drill stem, with the minor cutting edge being located, at a contemplated rotational direction of the drill about its axis, in front of a corresponding major cutting edge adjacent to a main discharge groove for drilling dust.
2. Description of the Prior Cut
In order to improve the cutting characteristics and the cutting capability, the rock drills are provided with major cutting edges, which usually extend over the diameter of a drill stem, and one or more minor cutting edges. The major and minor cutting edges are provided on cutting bodies which project beyond the end face of the drill stem and which are formed of a metal-cutting material, e.g., hard metal. The minor cutting edges are provided, e.g., on pin-shaped cutting bodies which are inserted, in addition to a major cutting edge-carrying cutting plate, in the end face of the drill stem or in the circumferential surface of the drill stem. In an alternative embodiment of a rock drill, the minor cutting edge or edges is/are provided on an elongate, plate-shaped, cutting body that projects from the end face of the drill stem and projects beyond the drill stem circumference. The elongate, plate-shaped, cutting body has a shape of an approximately ridge prism. In conventional rock drills, the arrangement of the minor cutting edges is so selected that they are located, at a contemplated rotational direction of a drill about its rotational axis, in front of an associated major cutting edge. As a result, the discharge of a drilling dust, which occurs during drilling, precedes respective minor cutting edges.
During drilling of bores in a reinforced concrete with such drills, it can occur that the drill, upon contacting the reinforcing iron, would be deflected, which can result in a bore shape that would deviate from a predetermined geometry of the bore. Further, the drill deflection can result in an unexpected passing of the torque peaks onto the user, and this causes, as a rule, interruption of the drilling process.
Accordingly, an object of the present invention, is to eliminate the drawbacks of the conventional rock drills by providing a rock drill capable of retaining its position during a sidewise encounter with a reinforcing iron.